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Spectroscopic and Thermodynamic Evidence of Dimer and Trimer Hydrogen Bonded Complex Formation between Chloroform and 2āButanone. Excess Molar Enthalpy for the Chloroform + 2āButanone Binary System at 303 K
FT-Raman
and FT-infrared spectra of pure chloroform (A) and 2-butanone
(B), as well as of the binary system chloroform + 2-butanone, were
recorded to investigate the type and nature of the intermolecular
complexes formed when both chemicals are mixed. The optimized structures
and vibrational frequencies for 2-butanone, chloroform, and their
1:1 and 1:2 complexes were calculated by means of density functional
theory (DFT) techniques using the B3LYP functional combined with the
6-31GĀ(d,p) and 6-311++GĀ(d,p) basis set. The recorded FTIR and Raman
spectra confirm the existence of these types of hydrogen-bonded complexes,
making it possible, furthermore, to calculate the heteroassociation
constants. Heat of mixing at 303 K over the whole mole fraction range
at atmospheric pressure was also measured. The excess molar enthalpy
was fitted to a RedlichāKister-type equation, using least-squares
to obtain its dependence on concentration. The ideal associated solution
model was also used to calculate these equilibrium constants among
the chemical species in solution, which compare well with that calculated
with the spectral determinations and the enthalpy of hydrogen bond
formation. Furthermore, the McGlashanāRastogi linearization
test was also used to provide thermodynamic evidence about the stoichiometry
of the formed complexes